Hydraulically-operated reciprocating apparatus



lJune 1, 1965 J, U. HAUSER "3,186,169

HYDRAULICALLY-OPERATED RECIPROCATING APPARATUS Filed NOV. l2 1963 -I- l F76. 25

VENTO? Jon NES U. HAUSEQ United States Patent Office Patented June 1, 1965 3,186 169 HYDRAULICALLY-OPERTED RECIPROCATING APPARATUS Johannes Ulrich Hauser, Nussbaurnen, Aargau, Switzerland, assignor to Keelavite Hydraulics Limited, Warwickshire, England, a company of Great Britain Filed Nov. 12, 1963, Ser. No. 322,652 Claims priority, application Great Britain, Dec. 3, 1962, 45,665/ 62 4 Claims. (Cl. 641-51) This invention relates to hydraulically operated reciprocating apparatus of the kind comprising a double-acting working piston and cylinder assembly, providing two working chambers, the pressures in which respectively act on the piston in opposite directions relative reciprocation between the working piston and cylinder being caused by the operation of control valve apparatus which controls the supply of working liquid under pressure to and the escape of working liquid from at least one of said working chambers so as to vary the relationship between the pressures respectively in the two working chambers.

While the invention is applicable to hydraulically operated reciprocating apparatus of the above kind, in general, it is particularly applicable to the hydraulically operated reciprocating apparatus of this kind forming the subject of the present applicants United States Patent No. 2,887,776 granted May 26, 1959.

An object of the invention is to provide a form of hydraulically operated reciprocating apparatus of the kind in question in which one of the two working chambers has a substantially smaller cross sectional area than the other and wherein the effective circumferential length f the leakage path from said working chamber represented by the working clearances between the relatively reciprocating parts which co-operate to form the chamber will be small as compared with known constructions. l

Hydraulically operated reciprocating apparatus of the kind referred to according to the present invention comprises a main working piston and cylinder assembly including a main working cylinder and a main working piston having a part of larger diameter disposed for reciprocation Within the main working cylinder and co-operating therewith to form a irst working chamber of larger cross sectional area, a subsidiary working piston and cylinder assembly comprising a subsidiary working piston and a subsidiary working cylinder arranged for reciprocation relatively to one another, one of such relatively moving parts being rigid with the main working piston while the other is rigid with the main working cylinder, the subsidiary working cylinder opening into the end of the main working cylinder remote from the said working chamber of larger cross-sectional area and being of smaller cross-sectional area than said working chamber of larger cross-sectional area, uid pressure means comprising at least one source of fluid pressure, passage means connecting said iiuid pressure means continuously to said working chamber of smaller cross-sectional area, relief passage means, and valve means operating to connect said working chamber of larger cross-sectional area alternately to said iiuid pressure means and to said relief passage means.

One construction according to the invention is 'shown somewhat diagramm'atically by way of example in the accompanying drawings as applied to apparatus also embodying the invention forming the Vsubject of the present applicants above United States application, in which drawings Y FIGURE 1 is a sectional side elevation of the apparatus as a whole with the working piston in one end position, and

FIGURE 2 is a similar view to FIGURE 1 on an enlarged scale showing only the working piston and cylinder assembly showing the working piston in its other end position.

In the construction shown in the drawings the apparatus comprises a main working piston and cylinder assembly including a main working cylinder 1 containing a main working piston 2 arranged to reciprocate therein and having formed thereon three lands, 3, 4 and 5, making sliding engagement with the cylinder 1 while a projection '6 extends through a cylindrical bore of smaller diameter than the lands 3, 4 and 5 to constitute a part by which a percussive tool can be actuated. The arrangement thus provides an annular working chamber 7 constituting a working chamber 0f larger cross-sectional area, the pressure in which urges the working piston 2 to the right. The working chamber of smaller crosssectional area, the pressure in which urges the Working piston 2 to the left, is in the form of a cylinder 8 formed in a part of the working piston 2 as shown and having extending into it a tubular piston 9 which, with the cylinder 8, constitutes a subsidiary piston and cylinder assembly providing the working chamber of smaller cross-sectional area 8.

Opening into the working chamber 7 of larger crosssectional area is a combined inlet and outlet port 10 communicating with a port 11 in the wall of a valve chamber 12 containing a reciprocating valve 13 constituting a control valve by which the port 11 can be connected alternately to a source of iluid pressure, hereinafter described, by way of a working liquid delivery passage 14 and to a relief passage 15. The end of the Working cylinder 1 remote from the Working chamber 7 is connected through a further relief passage 16 and a non-return valve 17 to the relief passage 15, While a port 18 in the main working cylinder 1 is connected by a passage 19 to the relief passage 15, and ports 20 and 21 in the main working cylinder 1 are connected respectively to pressure chambers 22 and 23 at the ends of the valve chamber 12.

The fluid pressure apparatus providing working liquid under pressure for causing reciprocation of the working piston 2 in the cylinder 1 comprises a continuously driven pump 24 arranged to draw liquid from a reservoir 25 and deliver it to the working liquid delivery passage 14, a return flow passage with a pressure relief valve 26 therein being provided to permit escape of surplus liquid from the delivery passage 14 via the passage 15 back to the reservoir 25, while maintaining a predetermined pressure within the delivery passage 14.

The delivery passage 14 also communicates with the liquid pressure chamber 27 of a rst hydraulic accumulator device 28 of the well-known gas-loaded -type into and out of which hydraulic accumulator working liquid can therefore flow respectively during the periods when the supply of working liquid to the port 11 via the valve 13 is interrupted and during the periods when such ow is taking place.

Also connected to the delivery passage 14 through la non-return valve 29 is the liquid ychamber of a further hydraulic accumulator 30 also `of the gas-loaded type and having a piston 31 dividing the :liquid chamber from the gas chamber 32 in which a predetermined mean gas pressure can be established. The liquid cham-ber of the hydraulic .accumulator 30 communicates continuously and directly by way lof an Iopenpassage 33 with the cylinder 8 which constitutes the subsidiary Workin-g chamber.

`In FIGURE .1 the main working piston 2 is shown at the right hand end .of its travel, while the valve 13 occupies the position into which it will just have moved due to the working piston having reached such end of its travel, and FIGURE 2 shows the working piston at the 3 left hand end of its travel. `The operation of the apparatus is as follows:

Assuming the working piston 2 to be in the position shown in FIGURE l, it will be seen that the chamber 22 is connected, via the passage 21 yand the space between the lands 13 and 4 to the relief passage 15. Immediately prior to the moment when the working piston 2 reached the position shown in FIGURE 1 the valve 13 would have occupied its righthand position as hereinafter eX- plained, so that the ports and 11, and therefore the Working chamber 7, were at that time in communication with the delivery passage 14. At the moment, thereifore, when the yworking piston 2 reached its right hand end position shown in FIGURE 1, the passage 2t) -would have been brought into communication with the working chamber 7 while the latter was still subject to working pressure, through the port 11 with the result that this .working pressure was delivered also to the chamber 23 and the chamber 22 being in communication with the relief passage 15 as explained, the working pressure acted to move `the valve 13 into the lefthand position shown in FIGURE l.

In this position of the valve -it will be seen that the ports 10 and 11, and hence the working chamber 7, are in direct communication with the relief passage 15. In the manner hereinafter explained the piston 2 will now be moved to the left into the position shown in FIGURE 2, on reaching which it will be seen that, while the chamber 23 communicates (via the passage 20, the space between t'he lands 3 and `4, and the port 18) with the relief passage 15, the lpassage 21 and yhence the chamber 22 tare brought, kby way of a passage 34, in the piston 2 into communication with the cylinder 8 which, as hereinafter explained, lcontains iiuid under continuous pressure. Thus, the valve .13, is then caused to move to the right int-o the position shown `in FIGURE 1 thus again connecting the working chamber 7 to the delivery passage 14.

Liquid is maintained under pressure at all times during operation in the liquid chamber of the accumulator `39 by the pu-mp 24 via the non-return valve 29 and the pressure in such pressure chamber .will be increased .as the working piston 2 moves to the right, and liquid is thus displaced from the chamber 8 into the accumulator since the non-return valve 29 prevents such displaced liquid tbeing returned to the delivery -passage 14. Similarly the pressure in the pressure chamber of the accumulator 30 will drop as the piston `2 moves to the left under the -action of the pressure inthe chamber 8 but never apprecia'bly below that in the delivery pipe 14 since -on the occurrence lof any drop in pressure in the accumulator 30 below that in the passage 14 liquid will tlow through the valve 29 into the accumulator 30.

It will be understood that the capacity and dimensions of the accumulator 30 are such in relation to the stroke of the piston 2 and the cross-sectional area of the cylinder 8 that, with the minimum liquid pressure in the accumulator 3) maintained via the valve 29 at a value approximately equal to the pressure maintained in the delivery passage y14, the increases in the pressure in the accumulator 30 caused as the piston 2 moves towards and into its righthand position `are never such as to raise the pressure in the cylinder S to a value such that the force exerted by such pressure :on the piston 2 over the limited cross-sectional area of the chamber 8 will exceed the .force applied to the face of the land 3 (whi-ch constitutes the working face of the main working chamber 7) by the delivery pressure in the passage 14.

Thus, with the c-onstruction described the mean force with which the piston 2 is moved to the left is dependent upon the mean pressure maintained in the accumulator 30 and the relative dimensions of this accumulator and the cylinder and piston .assembly 8, 9 and the stroke of the piston 2, and can be varied by varying the mass of air in the chamber 32 of the accumulator and/or the pressure maintained in the delivery passage 14.

`It is desirable for the non-return valve 29 to be provided with a slight by-pass leak so that, while during normal operation it prevents ow of any appreciable quantity of -liquid past it into the passage 14 as the piston 2 moves to the right, it `will tend to provide for relatively slow changes in the mean pressure in the accumulator Sil with changes in the pressure maintained in the passage 14. By this means, within a considerable range lthe delivery pressure in the passage ,14 may be varied to vary the force ywith which 4the piston 2 is moved to the left without disturbing the operation of the apparatus because any maintained change in pressure in the passage 14 automatically causes a corresponding change in the mean pressure in the accumulator 30 .as well as changing the pressure available for delivery to the working chamber 7.

What I claim as my invention land desire `to secure by Letters Patent is:

1. Hydraulically operated reciprocating apparatus comprising a main working piston .and cylinder assembly including a main working cylinder and a main working piston having a part of larger diameter disposed for reciprocation within the main working cylinder and cooperating therewith to 'form a first working chamber of larger cross-sectional area, a subsidiary working piston and cylinder assembly comprising a subsidiary Working piston .and a subsidiary working cylinder arranged for reciprocation relatively to one another, one of such relatively moving parts 'being rigid with the main Work-ing piston while the other is rigid with the main working cylinder, the subsidiary working cylinder opening into the end of the main working cylinder remote from the said working chamber of larger cross-sectional area and being of smaller cross-sectional area than said working chamber of larger cross-sectional area, lluid pressure supply means, passage means connecting said fluid pressure supply means continuously to said working chamber of smaller cross-sectional area, a hydraulic accumulator having its liquid pressure chamber connected to said passage means, a non-return valve between said liquid pressure chamber tand the part of said passage means between said -luid pressure supply means `and said liquid pressure chamer to permit liquid to flow from said fluid pressure supply means into said liquid pressure chamber but not out of said liquid pressure chamber towards said uid pressure supply means', while open passage means continuously connect said liquid pressure chamber of said hyldraulic accumulator to said subsidiary working cylinder, relief passage means, and valve means operating t-o connect said working chamber of larger cross-sectional area alternately to said uid pressure supply means and to said relief passage .me-ans.

2. Hydraulically operated reciprocating apparatus as claimed in claim 1, in which said uid pressure supply means comprises `a pump having a delivery passage communicating with said valve means and through s-aid nonreturn valve, .with said liquid pressure chamber of said accumulator device.

3. Hydraulically operated reciprocating apparatus as claimed in claim 2 including a second yhydraulic accumulator connected to and in continuous open communication with the delivery passage of said pump.

4. Hydraulically operated reciprocating apparatus as claimed in claim 1 including an automatic relief valve permitting escape of iiuid from the end of said main working cylinder remote from said Working chamber of larger cross-sectional area.

References Cited by the Examiner UNITED STATES PATENTS 7/36 Helenberg 60-52 X 2,731,796 1/56 Sublett et al. 60--51 JULIUS E. WEST, Primm-y Examiner. EDGAR w. GEOGHEGAN, Examiner. 

1. HYDRAULICALLY OPERATED RECIPRICATING APPARATUS COM PRISING A MAIN WORKING PISTON AND CYLINDER ASSEMBLY INCLUDING A MAIN WORKING CYLINDER AND A MAIN WORKING PISTON HAVINGA PART OF LARGER DIAMETER DISPOSED FOR RECIPROCATION WITHIN THE MAIN WORKING CYLINDER AND COOPERATING THEREWITH TO FORM A FIRST WORKING CHAMBER FOR LARGER CROSS-SECTIONAL AREA, A SUBSIDIARY WORKING PISTON AND CYLINDER ASSEMBLY COMPRISING A SUBSIDIARY WORKING PISTON AND A SUBSIDIARY WORKING CYLINDER ARRANGED FOR RECIPROCATION RELATIVELY TO ONE ANOTHER, ONE OF SUCH RELATIVELY MOVING PARTS BEING RIGID WITH THE MAIN WORKING PISTON WHILE THE OTHER IS RIGID WITH THE MAIN WORKING CYLINDER, THE SUBSIDIARY WORKING CYLINDER OPENING INTO THE END OF THE MAIN WORKING CYLINDER REMOTE FROM THE SAID WORKING CHAMBER OF LARGER CROSS-SECTIONAL AREA AND BEING OF SMALLER CROSS-SECTION AREA THAN SAID WORKING CHAMBER OF LARGER CROSS-SECTIONAL AREA, FLUID PRESSURE SUPPLY MEANS, PASSAGE MEANS CONNECTING SAID FLUID PRESSURE SUPSUPPLY MEANS CONTINUOUSLY TO SAID WORKING CHAMBER OF SMALLER CROSS-SECTIONAL AREA, A HYDRAULIC ACCUMULATOR HAVING ITS LIQUID PRESSURE CHAMBER CONNECTED TO SAID PASSAGE MEANS, A NON-RETURN VALVE BETWEEN SAID LIQUID PRESSURE CHAMBER AND THE PART OF SAID PASSAGE MEANS BETWEEN SAID FLUID PRESSURE SUPPLY MEANS AND SAID LIQUID PRESSURE CHAMBER TO PERMIT LIQUID TO FLOW FROM SAID FLUID PRESSURE SUPPLY MEANS INTO SAID LIQUID PRESSURE CHAMBER BUT NOT OUT OF SAID LIQUID PRESSURE CHAMBER TOWARDS SAID FLUID PRESSURE SUPPLY MEANS, WHILE OPEN PASSAGE MEANS CONTINUOUTSLY CONNECT SAID LIQUID PRESSURE CHAMBER OF SAID HYDRAULIC ACCUMULATOR TO SAID SUBSIDIARY WORKING CYLINDER, RELIEF PASSAGE MEANS, AND VALVE MEANS OPERATING TO CONNECT SAID WORKING CHAMBER OF LARGE CROSS-SECTIONAL AREA ALTERNATELY TO SAID FLUID PRESSURE SUPPLY MEANS AND TO SAID RELIEF PASSAGE MEANS. 